Where someone works in term time but not in the school holidays (eg teaching assistants) the HB regulations do not stipulate whether HB should be based on different income figures for holidays and term time or average them over the year.
However the general view taken is that it depends on the basis on which a term time only worker is employed, ie that:
if the employment is for term time only and
a) there is no retainer payable during the holiday period and
b)there is no real certainty that the person will be asked to return to work for the next term -
then earnings and hours would only be taken into account over the term time (ie when they're actually working.
This might mean they would be eligible for HB in holidays only. So if HB ends, when they need to get help with their housing costs again, then in a Full Service UC area they would need to claim UC instead.
But where either
a) a retainer is paid, or
b) the employment is on the basis that there is an expectation they will return every term -
- the HB Office would treat the holiday periods as part of a "recognisable cycle" and average both earnings and hours over a whole period of both term time and holidays.
Note that if they are on Working Tax Credit, again how their hours and earnings are treated depend on the same principle - ie where there is a recognisable pattern of work HMRC average out the earnings over the year.
But in terms of whether the person is working enough hours to qualify, where it's a recognisable pattern of work HMRC will ignore the fact that they are not actually working in the holidays and treat them as being on the same number of hours as when working - ie treat them as in remunerative work (and thereby eligible for Working Tax Credit).